Look, really, tell him that telnet is unavailable. If someone is still making software that requires telnet, then he does not want to have anything to do with them. Anything that needs shell-ish access should be using ssh, without exception.

OK, you can, it is as simple as uncommenting a line in /etc/inetd.conf, but you really, really, do not want to.

__________________The only dumb question is a question not asked.
The only dumb answer is an answer not given.